This invention relates to a radio communication apparatus for receiving a selective call signal which includes message data with a transmission number. The communication apparatus may be a radio paging receiver, a transceiver, or the like although description will mainly directed to the radio paging receiver.
A radio paging system comprises a plurality of radio paging receivers and a plurality of base stations each for transmitting a selective call signal. A radio paging receiver of the type described includes a receiving circuit for carrying out a receiving operation of selectively receiving the selective call signal specific to the apparatus The receiving circuit produces a received signal whenever the receiving circuit receives the selective call signal.
Various radio paging receivers of the type are already known. By way example, a pager is disclosed in U.S. Pat. No. 4,412,217 (which will be herein called reference 1) issued to David P. Willard et al. on Oct. 25, 1983 which is hereby incorporated herein by reference. The pager according to Willard et al. is a pager with visible display indicating status of memory.
The selective call signal may include message data with a transmission number. In this event, the radio paging receiver receives the massage data with the transmission numbers. The transmission number is a number where the system administers transmission order for message data. The transmission numbers are assigned to addresses and the radio paging receiver ascertains whether or not the transmission numbers attached to the massage data are put in order. If the transmission numbers are not put in order such that the transmission numbers skip or the transmission numbers reverse the order, the radio paging receiver generates an alert signal indicative of omission of message. Accordingly, it is possible to notify a user of the radio paging receiver of occurrence of the omission of message.
In the radio paging system of the type described, when the user detects the omission of the message, the user telephones an operator to request retransmission of message. In this event, no problem arises if the message data to be retransmitted is attached with the transmission number which is more than that of the latest message data by one on retransmission of the message having an omitted transmission number.
However, there is a radio paging system where the base station transmits the message data with the same transmission number attached thereto the last time on retransmission. Such a radio paging system is, for example, European Radio Message System (ERMES). Under the circumstances, alert of message omission is carried out on reception of a retransmitted message, although the message omission does not occur actually. This is because the transmission numbers do not continue. Accordingly, such a radio paging system is disadvantageous in that it is difficult for the user to operate and it results in carrying out alert of the message omission erroneously.
In order to resolve the above-mentioned problem, a radio paging receiver is published in Japanese Unexamined Patent Publication of Tokkai No. Hei 6-120,869 or JP-A 6-120,869 (which will be herein called reference 2) on Jun. 28, 1994 which is hereby incorporated herein by reference. The radio paging receiver according to JP-A 6-120,869 comprises a receiver/demodulator, a decoder, a CPU, a massage memory, a buffer, a register, a reception omission alert signal generator, an amplifier, and a speaker. The receiver/demodulator receives and demodulates a selective call signal which is sent from a base station and which includes a call signal and a message signal. The decoder decodes, as decoded signals, the call signal and the message signal from the selective call signal. The decoder decides whether these decoded signals are addressed to its own or not. The CPU stores the message addressed to its own in the message memory and also stores temporarily, as a current transmission number, the transmission number for message in the buffer. A transmission number for message immediately before reception is held in a register as a previous transmission number. The CPU calculates a difference between the current transmission number and the previous transmission number by subtracting the previous transmission number from the current transmission number. When the calculated difference is equal to two or more, a reception omission alert signal is produced by the reception omission alert signal generator. An audible tone indicative of the reception omission of a message is generated by the speaker through the amplifier.
However, in the above-mentioned radio paging system, other message data are assigned with different transmission numbers. In addition, the same transmission number is assigned to the same message data on transmission several times or on retransmission. As a result, the message data for the transmission several times or for the retransmission interrupt in the radio paging receiver during reception of message data having serial transmission numbers. Accordingly, the above-mentioned reference 2 has a problems that the audible tones generate frequently.